The present invention relates to a pushbutton switch, and more specifically, a pushbutton switch having a contact point, which is activated by an axially disposed cam.
Various forms are proposed as a pushbutton switch in which a contact point is activated by an axially disposed cam.
For example, a pushbutton switch as shown in FIG. 13 to FIG. 19 is proposed in JP-A-2-72526. FIG. 13 illustrates an exploded perspective view of a pushbutton switch defined in JP-A-2-72526. It includes an actuator housing 101 having a substantially cylindrical passage 101a in which a pushbutton 100 and the like, as below-mentioned, is contained. The pushbutton 100 has a cylindrical-shaped cylinder portion 100a (FIG. 15B) which is engaged with the passage 101a. An actuator cam follower 102 has a square shaped internal cavity portion 102a with a square columnar shape inside, where a rotary contact carrier 104 (as hereinafter referred) is fitted loosely onto. An actuator return spring 103 which is interposed between the actuator cam follower 102 and the rotary contact carrier 104, as described below, is intended to upwardly urge the actuator cam follower 102, or downwardly urge the rotary contact carrier 104. The rotary contact carrier 104, which has a stem 104a fitted loosely onto the square shaped internal cavity portion 102a, is rotated in the flat surface portions according to a predetermined angle rotary motion of the actuator cam follower 102 to allow the rotary contact element 105 in the bottom to effect an electric connection as referred below and electrical isolation of the electric contact elements 106a, 106b, and 106c as referred below, and performs alternating ON/OFF switching action. A stationary contact housing portion 106 has electric contact elements 106a, 106b, and 106c arranged in predetermined form. A coveting part 107 covers the bottom of the pushbutton switch.
The main element members of the pushbutton switch described in JP-A-2-72526 will be discussed hereinafter.
FIG. 14 is a sectional view of an actuator housing 101. A cylindrical passageway 101a with which a pushbutton 100 is engaged, is formed in the actuator housing 101. Pushbutton guides 101b in the profile of a projection along the longitudinal direction are formed at an equal spacing in the inner surface of this passage 101a. Adjoining pushbutton guides 101b and 101b are separated by guide portions 101c which are recessed grooves. The lower ends of such pushbutton guides 101b are formed in slant surfaces, and serve as cam surfaces 101d. 
FIG. 15A is a side view of a pushbutton 100, and FIG. 15B is a sectional view of a pushbutton 100. The pushbutton 100 is a hollow cylindrical member having a cylindrical-shaped cylinder portion 100a inside thereof. Four slide guides 100b (only three of them are displayed in FIG. 15A) are disposed in lower end portions at 90-degree-intervals extending outwardly in the radial direction. These slide guides 100b are slidably engaged with the guide recess portions 101c (FIG. 14), and guide a pushbutton 100 linearly at the time of reciprocating motion of the pushbutton 100. The lower end portions of a pushbutton 100 are formed into saw teeth. Each saw tooth 100c consists of apex 100d and slant-shaped cam sides 100e which surround the apex 100d. Eight saw teeth 100c are disposed in the lower end portions of the pushbutton 100, equally spaced at 45 degree intervals.
As shown in FIG. 15B, the central axis of the slide guide 100b (FIG. 15) is provided to pass through the apex 100d of each saw tooth 100c. 
FIG. 16A is a side view of an actuator cam follower 102, and FIG. 16B is a sectional view of the actuator cam follower 102. The actuator cam follower 102 is a hollow cylindrical member which has a circular opening and a square columnar shaped internal cavity portion 102a in the square columnar shape inside thereof, as shown in FIG. 16B.
The actuator cam follower 102 is a member slidably fittingly mounted into the cylindrical cylinder portion 100a (FIG. 15B). Also, predetermined angle rotation is carried out by the cam action as hereinafter referred, while performing a vertical movement along with the reciprocating motion of the pushbutton 100, so that a translating mechanism that converts linear motion of a pushbutton to rotary motion is achieved.
The lower part of actuator cam follower 102 is adapted to a diameter expansion part 102b, the diameter of which is expanded. A saw tooth 102c, which has the same form as a saw tooth 100c (FIGS. 15A and 15B), is provided at the upper end of this diameter expansion part 102b. The saw tooth 102c consists of the apex 102d and slant-shaped cam sides 102e which surround the apex 102d. Further, from a diameter expansion part 102b of an actuator cam follower 102, cam follower guides 102f extend outwardly in the radial direction spaced at a 90 degree interval.
The central axis of the slide guides 100b (FIG. 15A) of the pushbutton 100 are provided to pass through the apex 100d of each saw tooth 100c, whereas, the central axis of the cam follower guides 102f are provided to be offset from the apex 102d of the saw tooth 102c slightly.
FIG. 17 is a side view of a rotary contact carrier 104. The rotary contact carrier 104 is a member including a rotary contact element 105 which consists of a square columnar stem 104a formed in a tapered twisted end in the upward direction, and a substantially circular metal plate provided in the bottom of this stem 104a. 
A rotary contact carrier 104 is a member wherein a stem 104a is slidably engaged with a square shaped internal cavity portion 102a (FIG. 16B). Rotation of an actuator cam follower 102 accompanying reciprocal operation of a pushbutton 100 is transmitted to the stem 104a through the square shaped internal cavity portion 102a. Then, a rotary contact element 105 carries out predetermined angle (predetermined-number-step) rotation with the result that the electric connection and electrical isolation of the electric contact elements 106a, 106b, and 106c, which are the electrodes provided in the stationary contact housing portion 106 (FIG. 13), are affected. Then, alternate ON/OFF switching action is affected.
Incidentally, lubricant, such as grease, is applied to the inner part of the stationary contact housing 106 to thereby allow electric contact elements 106a, 106b, and 106c to be in less friction with a rotary contact element 105 at the time of sliding rotation.
Next, operation of a pushbutton switch disclosed in a JP-A-2-72526 will be discussed.
FIG. 18 is a schematic diagram, wherein cam mechanism constituted by an actuator housing 101, a pushbutton 100, and an actuator cam follower 102 is deployed in a plane view.
FIG. 18A is a diagram showing the state where the pushbutton 100 is not pressed. The pushbutton 100 and the actuator cam follower 102 are urged upwardly by an actuator return spring 103 (not shown) and are fixed. Hereafter, this state is referred as upper dead center. In the upper dead center, slide guides 100b (FIG. 15A and FIG. 15B) and cam follower guides 102f (FIG. 16) are engaged with guide recess portions 101c (FIG. 14). Further, a saw tooth 100c of a pushbutton 100 and a saw tooth 102c of an actuator cam follower 102 contact with each other by mutual cam sides 100e and 102e with a state that the phase thereof is offset. This is because, as described hereinbefore, in a pushbutton 100, the central axis of slide guides 100b is provided to pass through the apex 100d (FIG. 15A), whereas in an actuator cam follower 102, the central axis of the cam follower guides 102f is provided to be offset from the apex 102d of a saw tooth 102c (FIG. 16A).
When a pushbutton 100 is pressed to descend and lower, dead center is reached, resisting the opposing force of an actuator return spring 103, and the actuator cam follower 102 is guided by guide recess portions 101c, and moves below. When projections of cam follower guides 102f cross over the tip part of slant cam surfaces 101d in due course, the actuator cam follower 102 is separated from the guidance of guide recess portions 101c to slide on cam side 100e by the opposing force of the actuator return spring 103, and moves (rotates) by distance X (leftward in the figures) to enable a saw tooth 100c of a pushbutton 100 and a saw tooth 102c of an actuator cam follower 102 to be engaged with a state of the phase thereof to be in agreement (FIG. 18B). When the phase of a saw tooth 100c and a saw tooth 102c is in agreement, sound is caused by the pressing (a click of a latch) as the cam sides 100e and cam sides 102e collide.
According to FIG. 19, when the pushbutton 100 is released after the termination of a button-pressing action of the pushbutton 100, the pushbutton 100 and the actuator cam follower 102 go up rapidly by an opposing force of an actuator return spring 103. By this rise, the cam follower guide 102f collides with slant cam surfaces 101d to move (rotate) by distance Y, which is bigger than distance X, leftward in the figure, sliding on the cam surfaces 101d. At the time of the rotation of this distance Y, a rotary contact carrier 104 engaged with an actuator cam follower 102 is rotated greatly to effect the ON/OFF switching action.
A cam follower guide 102f, being engaged with guide recess portions 101c-B in due course, goes up rapidly while guided by a guide recess portions 101c-B, and results in upper dead center. In the upper dead center, when cam sides 100e and cam sides 102e collide, the return sound xe2x80x9ca click of a latchxe2x80x9d occurs.
According to FIG. 19, when a pushbutton 100 is released after the termination of a button-pressing action of a pushbutton 100, a pushbutton 100 and an actuator cam follower 102 go up rapidly by the opposing force of the actuator return spring 103. By this rise, a cam follower guide 102f collides with slant cam surfaces 101d, and moves (rotates) leftward by bigger distance Y than distance X sliding on cam surfaces 101d. At the time of the rotation of this distance Y, the rotary contact carrier 104 engaged with the actuator cam follower 102 rotates greatly, so as to effect the ON/OFF switching action.
A cam follower guide 102f will engage with guide recess portions 101c-B in due course, going up rapidly while guided by guide recess portions 101c-B, and results in upper dead center. In the upper dead center, when cam sides 100e and cam sides 102e collide, it sounds like xe2x80x9ca click of a latchxe2x80x9d.
According to an important feature of the invention disclosed in JP-A-2-72526, alternating position ON/OFF of a switch is defined when a pushbutton 100 returns to upper dead center from lower dead center. If this is checked with a user""s movement, when the user presses a pushbutton 100, the pressing sound of xe2x80x9ca click of a latchxe2x80x9d can be heard first. However, in this stage, alternating ON/OFF switching position is not defined, but if a button is pressed as far as reaching the lower dead center and a hand is lifted, the return sound xe2x80x9ca click of a latchxe2x80x9d can be heard after that.
Thus, a user""s feeling of operation and alternating ON/OFF position of the pushbutton switch disclosed in JP-A-2-72526 do not match. Therefore the user may have a sense of incongruity.
This has posed a technical problem to be solved. This invention provides a pushbutton switch wherein alternating ON/OFF position of a switch is defined simultaneously with a press sound of the press button. In addition, in the reciprocal motion of the press button, alternating ON/OFF position of the switch can be effected at any time at will.
Also, a pushbutton switch disclosed in JP-A-2-72526 generates a return sound of xe2x80x9ca click of a latchxe2x80x9d by collision of cam sides 100e and cam sides 102e in the upper dead center caused by the opposing force of an actuator return spring 103 when a pushbutton 100 returns to the upper dead center from the lower dead center.
Hereupon, a pushbutton switch disclosed in JP-A-2-72526 has only one actuator return spring 103 to urge two members, as a pushbutton 100 and an actuator cam follower 102. This necessitates the pushbutton switch to employ a spring with large spring constant and strong opposing force. Therefore, a problem arises that the return sound emitted by the collision of cam sides 100e and cam sides 102e is loud.
These are the problems to be solved by this invention.
The present invention is provided to overcome the above discussed problems in the below-mentioned manner.
The invention provides a pushbutton switch that includes a case having an substantially cylindrical-shaped cylinder portion. A substantially cylindrical button is fittingly mounted into the cylinder portion so as to be capable of a sliding motion along the cylinder portion. A substantially cylindrical rotor having a flange at the bottom performs a sliding reciprocating motion along the cylinder portion while carrying out predetermined angle rotation in the predetermined direction by setting the rotation axis as the long axis of the cylinder portion. A substantially toroidal plate contact segment is inserted by the rotor to be latched by the rotor. A plurality of stationary terminals are provided in the case opposed to the contact segment.
The rotor carries out predetermined angle rotation for every reciprocal motion of the button, then alternates ON/OFF switching positions which repeat the ON state where electrical contacts are effected between the fixed terminals and the contact segment, and the OFF state where electrical contacts are broken.
Tabular arms, which are formed into a curving shape in the direction of stationary terminals and contact with the stationary terminals spaced at predetermined intervals, are provided in the outer periphery portion of the contact segment. The arms are buckled elastically to retain the contact between the stationary terminals and the contact segment according to variation in distance from the stationary terminals to a rotor generated at the time of the reciprocal sliding of the rotor.
The alternating ON/OFF switching position of the pushbutton switch is defined by making a button to move reciprocately to cause a rotor to carry out predetermined angle rotation by changing the contact segment provided for the rotor into the state where electrical connection is broken from the state where electrical connection is made between stationary terminals. A pushbutton switch according to this invention provides a pushbutton switch in which by a button-pressing action, even if the distance between a rotor (contact segment) and stationary terminals spreads, the arms provided in the contact segment arc buckled so that electrical contact between stationary terminals and the contact segment may be retained. Hence, it becomes possible by changing the degree of deflection (curvature) of the arms to set up the timing of contact/non-contact state between stationary terminals and the arm at any time at will in a button-pressing action.
Also, it becomes possible by changing arrangement of stationary terminals to set up the timing of the alternating ON/OFF switching position of a pushbutton switch at any time at will in return operation of the button.
The invention may also include a first spring which urges the rotor upwardly and a second spring which urges the button upwardly.
Here, a pushbutton switch urges a button and a rotor upwardly with an independent spring respectively (a first spring and a second spring). Therefore, the spring with a smaller spring constant than a conventional one can be used as each spring, so that it becomes possible for the return sound emitted when the rotor urged by the first spring at the time of return operation of the button collides with other components to be smaller than a conventional pushbutton switch.
Further, even when a rotor urged by the first spring at the time of return operation of a button collides with other components, a part of this collision power is spent on making the arms of the contact segment provided for the rotor buckle between stationary terminals (arms work as a cushion so to speak). This makes it possible to weaken the collision power when a rotor collides with other components resulting in allowing the return sound to be smaller than a conventional pushbutton switch.
Projections may be arranged in the longitudinal direction, separated mutually by the guide recess portions in an inner periphery of the cylindrical portion spaced at predetermined intervals. The lower end of each projection serves as slant cylinder portion cam sides. Ribs which are fitted loosely into the guide recess portions are formed in the outer periphery of the lower ends of the button. The lower ends of the ribs constitute slant button cam sides having substantially the same inclination with the cylinder portion cam sides. Projections, which are fitted loosely into the guide recess portions, are formed in the upper ends of the rotor, and the upper ends of the projections serve as slant rotor cam sides having substantially inverse inclination with respect to the button cam sides. The cam sides perform a sliding movement to the cylinder portion cam sides by being pressed along the guide recess portions at the time of reciprocating motion of the button. The rotor cam sides carry out sliding movement along the button cam sides so that engagement with another adjoining guide recess may be achieved.
Ribs of the button and projections of a rotor are fitted loosely into the guide recess portions provided in inner peripheral surface of the cylinder portion. When a button-pressing action is performed, button cam sides provided in the lower end portions of the ribs are caused to press rotor cam sides provided in the upper ends of projections of the rotor. Along with this, the button .and the rotor perform a sliding movement downwardly along the guide recess portions. When projections of the rotor cross over the tip portions of slant cylinder portion cam sides in due course, the rotor cam sides slidingly carry out a predetermined angle rotation to move on the cylinder portion cam sides. At this time, xe2x80x9ca click of a latchxe2x80x9d is emitted.
When a button returns thereafter, rotor cam sides which were moving on the cylinder portion cam sides slide on the cylinder portion cam sides to engage with guide recess portions which are adjacent to above described guide recess portions while carrying out a predetermined angle rotation. At this time, a return sound of xe2x80x9ca click of a latchxe2x80x9d occurs.
Projections for a prevention of an excessive rotation, which are fitted loosely into the guide recess portions, may be provided along the longitudinal direction of the outer peripheral surface of the button.
These projections for a prevention of an excessive rotation which are fitted loosely into the guide recess portions of the cylinder portion are provided on the outer peripheral surface of a button. Whereby, a button always slides along guide recess portions, which obviates the disadvantage that when the button is excessively pressed, ribs of the button cross over the tip part of the cylinder portion cam sides, resulting in being rotated inadvertently to ride over cylinder portion cam sides.
A guide pole may extend along the central axis of the button from the lower end portion of the button. Then, in the case facing this guide pole, a cylindrical insertion portion having an opening, which has substantially the same diameter with that of guide pole, is provided.
A guide pole is extending from the lower end portion of the button, so as to be inserted in the insertion portion provided in the bottom of a case when a button-pressing action is performed. The guide pole is moved as guided by this insertion portion, in order to suppress vertically caused slight movement with respect to the central axis of the button.
Flat surface portions may be provided within the case, keeping contact with the contact segment. The terminal portions for connecting the external wiring to the pushbutton switch may be provided, wherein the terminal portions are extending downwardly from the flat surface portions into a shape of the letter xe2x80x9cUxe2x80x9d, as well as curving in spaced apart relation from the flat surface portions.
The terminal portions are curving from the flat surface portions into a shape of the letter xe2x80x9cUxe2x80x9d, and also are formed into a curving shape in spaced apart relation from the flat surface portions. Whereby, reliable external wiring can be maintained, irrespective of the form of the external wiring inserted in the terminal portions.
The stationary terminals are connected to a printed circuit board 9 (See FIG. 20), thereby providing for alternative electrical connections to a variety of applications.